1. Field of the Invention
The present invention concerns an improved method to produce an electrical energy storage device and the improved device. In the construction of the coated substrate to create the individual cells, a capillary tube and optionally a permselective polymer are incorporated into the edge polymer of the device. The capillary tube is useful to introduce the liquid electrolyte into this cell under vacuum conditions and for the accurate metering the amount of liquid electrolyte into the cell. The capillary is then sealed. The permselective polymer aids in the retention of the liquid electrolyte, but permits the permeation of gases which might be produced during the electrical charging and discharging of the cells. The devices so produced are useful at elevated temperatures, i.e., +85.degree. C. The present invention generally relates to an energy storage device, and more particularly to a bipolar double layer capacitor-type energy storage device, and to improved methods for manufacturing the same.
2. Description of the Related Art
Energy Storage Devices--There has been significant research over the years, relating to useful reliable electrical storage devices, such as a capacitor or a battery. Large energy storage capabilities are common for batteries; however, batteries also display low power densities. In contrast, electrolytic capacitors possess very high power densities and a limited energy density. Further, carbon based electrode double-layer capacitors have a large energy density; but, due to their high equivalent series resistance (ESR), have low power capabilities. It would therefore be highly desirable to have an electrical storage device that has both a high energy density and a high power density.
A review by B. E. Conway in J. Electrochem. Soc., vol. 138 (#6), p. 1539 (June 1991) discusses the transition from "supercapacitor" to "battery" in electrochemical energy storage, and identifies performance characteristics of various capacitor devices.
D. Craig, Canadian Patent No. 1,196,683, in November 1985, discusses the usefulness of electric storage devices based on ceramic-oxide coated electrodes and pseudo-capacitance. However, attempts to utilize this disclosure have resulted in capacitors which have inconsistent electrical properties and which are often unreliable. These devices cannot be charged to 1.0 V per cell, and have large, unsatisfactory leakage currents. Furthermore, these devices have a very low cycle life. In addition, the disclosed packaging is inefficient. Also, see D. Craig, European Patent 0 078 404.
M. Matroka and R. Hackbart, U.S. Pat. No. 5,121,288, discuss a capacitive power supply based on the Craig patent which is not enabling for the present invention. A capacitor configuration as a power supply for a radiotelephone is taught; however, no enabling disclosure for the capacitor is taught.
J. Kalenowsky, U.S. Pat. No. 5,063,340, discusses a capacitive power supply having a charge equalization circuit. This circuit allows a multicell capacitor to be charged without overcharging the individual cells. The present invention does not require a charge equalization circuit to fully charge a multicell stack configuration without overcharging an intermediate cell.
H. Lee, et al. in IEEE Transactions on Magnetics, Vol. 25 (#1), p.324 (January 1989), and G. Bullard, et al., in IEEE Transactions on Magnetics, Vol. 25 (#1) p. 102 (January 1989) discuss the pulse power characteristics of high-energy ceramic-oxide based double-layer capacitors. In this reference various performance characteristics are discussed, with no enabling discussion of the construction methodology. The present invention provides a more reliable device with more efficient packaging.
Carbon electrode based double-layer capacitors have been extensively developed based on the original work of Rightmire, U.S. Pat. No. 3,288,641. A. Yoshida et al., in IEEE Transactions on Components, Hybrids and Manufacturing Technology, Vol. CHMT-10, #1,P-100-103 (March 1987) discuss an electric double-layer capacitor composed of activated carbon fiber electrodes and a nonaqueous electrolyte. In addition, the packaging of this double-layer capacitor is revealed. This device is on the order of 0.4-1 cc in volume with an energy storage capability of around 1-10 J/cc.
T. Suzuki, et al., in NEC Research and Development, No. 82, pp. 118-123, July 1986, disclose improved self-discharge characteristics of the carbon electric double-layer capacitor with the use of porous separator materials on the order of 0.004 inches thick. An inherent problem of carbon based electrodes is the low conductivity of the material resulting in a low current density being delivered from these devices. A second difficulty is that the construction of multicell stacks is not done in a true bipolar electrode configuration. These difficulties result in inefficient packaging and lower energy and power density values.
Ultracapacitors provide one approach to meet the high power requirements for the advanced energy storage system for many uses, from cardiac pacemakers to cellular phones to the electric automobile. Until recently, the only packaged high power ultracapacitor material available for significant charge storage has been a mixed ruthenium and tantalum oxide (Z. W. Sun and K. C. Tsai, J. Electrochem. Soc. Ext. Abs., vol. 95-2, pp. 73-76 (1995) and R. Tong et al., U.S. Pat. No. 5,464,453 (1995)). Unfortunately, ruthenium and tantalum oxide are expensive.
Additional references of interest include, for example:
The state of solid state micro power sources is reviewed by S. Sekido in Solid State Ionics, vol. 9, 10, pp. 777-782 (1983).
M. Pham-Thi et al. in the Journal of Materials Science Letters, vol. 5, p. 415 (1986) discusses the percolation threshold and interface optimization in carbon based solid electrolyte double-layer capacitors.
Various disclosures discuss the fabrication of oxide coated electrodes and the application of these electrodes in the chlor-alkali industry for the electrochemical generation of chlorine. See for example: V. Hock, et al. U.S. Pat. No. 5,055,169 issued Oct. 8, 1991; H. Beer U.S. Pat. No. 4,052,271 issued Oct. 4, 1977; and A. Martinsons, et al. U.S. Pat. No. 3,562,008 issued Feb. 9, 1971. These electrodes, however, in general do not have the high surface areas required for an efficient double-layer capacitor electrode.
It would be useful to have a reliable long-term electrical storage device, and improved methods to produce the same. It would also be desirable to have an improved energy storage device with energy densities of at least 20-90 J/cc.
Packaging of Energy Storage Devices--As mentioned above, there has been significant research over the years regarding electrical storage devices of high energy and power density. The efficient packaging of the active materials, with minimum wasted volume, is important in reaching these goals. The space separating two electrodes in a capacitor or a battery is necessary to electrically insulate the two electrodes. However, for efficient packaging, this space or gap should be a minimum. It would therefore be highly desirable to have a method to create a space separator or gap that is substantially uniform and of small dimension (less than 5 mil (0.0127 cm).
A common way to maintain separation between electrodes in an electrical storage device with an electrolyte present (such as a battery or capacitor) is by use of an ion permeable electrically insulating porous membrane. This membrane is commonly placed between the electrodes and maintains the required space separation between the two electrodes. Porous separator material, such as paper or glass, is useful for this application and is used in aluminum electrolytic and double layer capacitors. However, for dimensions below 1 or 2 mil (0.00254 to 0.00508 cm) in separation, material handling is difficult and material strength of the capacitor is usually very low. In addition, the open cross-sectional areas typical of these porous membrane separators are on the order of 50-70%.
Polymeric ion permeable porous separators have been used in carbon double layer capacitors as discussed by Sanada et al. in IEEE, pp.224-230, 1982, and by Suzuki et al. in NEC Research and Development, No. 82, pp. 118-123, July 1986. These type of separators suffer from the problem of a small open area which leads to increased electrical resistance.
A method of using photoresist to fill voids of an electrically insulating layer to prevent electrical contact between two electrode layers for use as a solar cell is disclosed by J. Wilfried in U.S. Pat. No. 4,774,193, issued Sep. 27, 1988.
A process of creating an electrolytic capacitor with a thin spacer using a photosensitive polymer resin solution is disclosed by Maruyama et al in U.S. Pat. No. 4,764,181 issued Aug. 16, 1988. The use of solution application methods described with a porous double-layer capacitor electrode would result in the undesirable filling of the porous electrode.
Some additional specific references in this art include the following:
PCT/US93/08803, filed Sep. 17, 1993, Inventors: Tsai, K. C. et al., Int. Pub. No.: WO 94/07272, Int. Pub. Date: Mar. 31, 1994.
PCT/US95/03985, filed Mar. 30, 1995, Inventors: Tsai, K. C. et al., Int. Pub. No.: WO 95/26833, Int. Pub. Date: Oct. 12, 1995.
PCT/US95/15994, filed Dec. 11, 1995; Inventors: L. T. Thompson et al., Int. Pub. No. WO 96/19003, Int. Pub. Date: Jun. 20, 1996.
D. A. Evans, U.S. Pat. No. 4,992,910.
R. Marchand, et al., in U.S. Pat. No. 4,964,016.
Robert R. Tong, et al., U.S. Pat. No. 5,464,453.
Robert Tong et al., U.S. Pat. No. 5,384,685.
Additional U.S. Pat. Nos. of general interest also include 4,515,763; 4,851,206; 5,062,025; 5,079,674; 4,327,400; and 5,185,679.
Additional references of general interest include U.S. Pat. Nos. 3,718,551; 4,816,356; 4,052,271; 5,055,169; 5,062,025; 5,085,955; 5,141,828.
All of the applications, patents, articles, references, standards, etc. cited in this application are incorporated herein by reference in their entirety.
In view of the above, it would be very useful to have one or more methods to produce a reliable small space separation between electrodes in electrical storage devices with a large open cross-sectional area into which a defined amount of liquid electrolyte is added. It is also desirable to provide a method to selective remove gasses while retaining aqueous or non-aqueous electrolyte during operation. The present invention provides these methods.